The transportation, conveying, and handling of large quantities of aggregate materials such as coal can be difficult in cold weather, wherein cold temperatures can cause moisture present in or on the aggregate material to freeze to thereby bind the individual units of the aggregate material together to form a large mass. This phenomenon is referred to herein as “freeze-clumping.” Freeze-clumping can make it difficult to unload railcars or trucks containing coal or other aggregate materials. For instance, the coal can cause damage to hoppers and other receiving equipment. In addition, when unloading a railcar or truck, a large percentage of the load can stick to the bottom of the car or truck, causing further difficulties.
Heretofore, the prior art has taught to apply an anti-icing agent to the aggregate material and/or to the inside walls of the transporting equipment. The anti-icing agent is an agent that prevents or inhibits the formation of ice in or near the aggregate material. Generally, anti-icing agents may serve under proper conditions to remove ice or snow already present on a surface; this function is known as de-icing, and the same agents that are used for anti-icing often may be used for deicing. Anti-icing agents may be sprayed onto the coal as it is being handled by conveying equipment, such as a conveyor belt, prior to introduction into a railcar or truck. Alternatively, an anti-icing solution may be sprayed onto the pile of coal after it has been loaded onto the car or truck.
The prior art has provided various anti-icing agents. Chloride salts, in particular calcium and sodium chloride are commonly used, but these compounds suffer from a number of drawbacks. The principal drawback with such chloride salts is corrosivity of the conveying and transporting equipment, and also, in the case of coal, of the furnaces in which the coal is fired. In addition, sodium chloride is somewhat less effective at anti-icing than calcium chloride, but calcium chloride is more expensive. Commercial chloride salts may include significant amounts of heavy metals, which are of particular concern because they can adversely affect furnace components and can accumulate in the ash left over after coal combustion, thus causing disposal problems.
The prior art has also taught to treat coal with diesel fuel. Diesel fuel can be effective in inhibiting freeze-clumping of the coal, and adds combustible caloric content to the coal. However, diesel fuel can degrade conveyor belts used to convey the coal. Moreover, diesel fuel is a non-renewable resource, and can cause environmental problems if fuel drips off (or “leaches” out) of the coal.
Another class of anti-icing agents include glycols, in particular ethylene glycol and diethylene glycol. Although effective at some temperatures, these compounds are toxic, and also have a limited range of effective temperatures. Moreover, these glycols are costly.
It is desirable to provide a method for inhibiting freeze-clumping of an aggregate material such as coal with an anti-icing material that is less corrosive than an equivalent amount of chloride salt, and that is effective for its intended purpose. The anti-icing agent should not introduce large amounts of metals and other components into the aggregate material.
It is a general object of the invention to provide a method for inhibiting freeze-clumping of an aggregate material that, in preferred embodiments, satisfies these criteria.